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4.5.8. Debug Feature Register 0

The ID_DFR0 characteristics are:

Purpose

Provides top level information about the debug system in AArch32.

Usage constraints

This register is accessible as follows:

EL0

(NS)

EL0

(S)

EL1

(NS)

EL1

(S)

EL2

EL3

(SCR.NS = 1)

EL3

(SCR.NS = 0)

--RORORORORO

Must be interpreted with the Main ID Register, MIDR.

Configurations

ID_DFR0 is architecturally mapped to AArch64 register ID_DFR0_EL1. See AArch32 Debug Feature Register 0.

There is one copy of this register that is used in both Secure and Non-secure states.

Attributes

ID_DFR0 is a 32-bit register.

Figure 4.81 shows the ID_DFR0 bit assignments.

Figure 4.81. ID_DFR0 bit assignments

Figure 4.81. ID_DFR0 bit assignments

Table 4.168 shows the ID_DFR0 bit assignments.

Table 4.168. ID_DFR0 bit assignments
BitsNameFunction
[31:28]-

Reserved, res0.

[27:24]PerfMon

Indicates support for performance monitor model:

0x3

Support for Performance Monitor Unit version 3 (PMUv3) system registers.

[23:20]MProfDbg

Indicates support for memory-mapped debug model for M profile processors:

0x0

Processor does not support M profile Debug architecture.

[19:16]MMapTrc

Indicates support for memory-mapped trace model:

0x1

Support for Arm trace architecture, with memory-mapped access.

In the Trace registers, the ETMIDR gives more information about the implementation.

[15:12]CopTrc

Indicates support for coprocessor-based trace model:

0x0

Processor does not support Arm trace architecture, with CP14 access.

[11:8]-Reserved, RAZ.
[7:4]CopSDbg

Indicates support for coprocessor-based Secure debug model:

0x6

Processor supports v8 Debug architecture, with CP14 access.

[3:0]CopDbg

Indicates support for coprocessor-based debug model:

0x6

Processor supports v8 Debug architecture, with CP14 access.


To access the ID_DFR0:

MRC p15,0,<Rt>,c0,c1,2 ; Read ID_DFR0 into Rt

Register access is encoded as follows:

Table 4.169. ID_DFR0 access encoding
coprocopc1CRnCRmopc2
111100000000001010

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